It has already been proposed to use a carbodiimide compound as an end-sealing agent for a polymer compound having a terminal acid group such as a carboxyl group so as to suppress the hydrolysis of the polymer compound (Patent Documents 1 and 2). The carbodiimide compound used in this proposal is a linear carbodiimide compound.
When the linear carbodiimide compound is used as an end-sealing agent for a polymer compound, a compound having an isocyanate group is liberated by a reaction for bonding the linear carbodiimide compound to an end of a polyester to produce a smell peculiar to an isocyanate compound, thereby deteriorating work environment.
Patent Document 3 discloses a macrocyclic carbodiimide compound. Since this compound is produced as a highly diluted solution, the concentration of the macrocyclic carbodiimide compound is low, whereby it takes many days to react it with a polymer and therefore the utility of the macrocyclic carbodiimide compound as an end-sealing agent for polymers is low. Further, Patent Document 3 does not take into consideration the reduction of an isocyanate smell produced by the end-sealing of a polymer. This macrocyclic carbodiimide compound has a long chain, is readily decomposed at a high temperature and therefore is not suitable for use as an end-sealing agent for polymers having a high melting point such as polyesters.    (Patent Document 1) JP-A 2008-050584    (Patent Document 2) JP-A 2005-2174    (Patent Document 3) US-A 2008/0161554